Diabetes mellitus (diabetes) is a disease in which the body does not produce or properly use insulin. In simplest terms, insulin is a hormone needed to convert sugar and starches into energy. In effect, insulin is the hormone that unblocks cells of the body, allowing glucose to enter these cells to provide food to keep them alive. If glucose cannot enter the cells, the glucose concentration in the body builds up and, without treatment, the cells within the body end up starving to death. The measurement of blood-glucose is thus perhaps the most important measurement in medicine, as diabetes has immense public health implications. Diabetes is currently a leading cause of disability and death throughout the world.
Diabetes sufferers cannot moderate the amount of glucose in their bloodstream automatically in the manner non-sufferers can. Therefore to prevent the onset and the progression of complications associated with diabetes, sufferers of both Type I (where the body fails to produce sufficient insulin) and Type II diabetes (where the body develops a resistance to the action of its own insulin) are advised to closely monitor the concentration of glucose in their bloodstream. If the concentration is outside the normal healthy range, the patient needs to adjust his or her insulin dosage or sugar intake to counter the risk of diabetic complications.
The most common method of measuring blood-glucose level requires blood to be withdrawn from the patient. The conventional procedure involves pricking the finger, or other body part, to withdraw blood, and then to test the blood for glucose levels, either by depositing one or more drops onto a reagent carrier strip having a glucose testing substance thereon that changes colour or shading in correspondence with the detected amount of blood-glucose, or by the use of a portable, often hand held, electronic testing device. However, many people find this method either inconvenient, painful, difficult to perform or simply unpleasant.
A further common glucose monitoring method involves urine analysis. This method tends to be most inconvenient and may not reflect the current status of the blood-glucose level due to the fact that glucose appears in the urine only after a significant period of elevated levels of blood-glucose.
Another technique involves using implantable medical devices to measure cardiac signals. In one such invention, the blood-glucose levels are determined based on T-wave amplitude and the QT-interval. The disadvantage of this method is that the instrument has to be inserted inside the human body and so a complex medical procedure may need to be performed. Also, the patient would need to be admitted to hospital and may need to stay for a few days. Additionally, this device would be classified as a class III medical device because it is inserted inside the body. A class III medical device is categorised as a high-risk device and would need to go through stringent testing and validation procedures before being granted approval by the medical devices regulatory bodies to enable it to be put into regular use.
A further measurement technique involves the sampling of interstitial fluid from the skin. A system developed by Cygnus Inc., known as the GlucoWatch G2 Biographer, uses low levels of electrical current to extract glucose molecules through the skin. The glucose is extracted from interstitial fluid that surrounds skin cells, rather than from blood. The system gathers and analyses current-time and charge time data to calculate blood-glucose level information. The drawbacks of this system are; it is still necessary to perform the finger prick test in order to calibrate the system and it is still necessary to withdraw a small amount of biological fluid (interstitial fluid) from the body during normal operation.
Many attempts have also been made to develop a painless, patient friendly, cost effective, non-invasive instrument to monitor blood-glucose levels. The non-invasive approaches considered include: electrochemical, spectroscopic technologies, such as near infrared spectroscopy, Ramen Spectroscopy and small scale NMR, measurements on lacrimal fluid (self-sampled tears), and acoustic velocity measurement techniques. However, none of these methods appear to have produced a marketable device or method for in-vivo measurement of blood-glucose level that is sufficiently accurate, reliable, patient friendly, convenient and cost-effective enough to be used in routine use.